Association between sleep patterns and alcohol use disorders in workers

Alcohol use among workers that is intended to aid sleep may lead to alcohol use disorders. This study aimed to explore the association between sleep patterns and alcohol use disorders in workers. Data from the Korea National Health and Nutrition Examination Survey conducted in 2014, 2016, 2018, and 2020 were used for this study. We included only workers aged 19 years and older. The final analysis comprised 11,972 respondents (6,472 male and 5,500 female). Multiple logistic regression analysis was used to investigate the relationship between sleep patterns and alcohol use disorders. Workers with poor sleep patterns were more likely to develop alcohol use disorders compared to those with good sleep patterns (male: adjusted odds ratio [OR] 1.22, 95% confidence interval 1.07–1.39; female: adjusted OR 1.21, 95% CI 1.03–1.41). Workers with both poor sleep quality and less than seven hours of sleep had the highest odds of alcohol use disorders in both male (adjusted OR 1.73, 95% CI 1.38–2.17) and female (adjusted OR 1.44, 95% CI 1.13–1.84). Poor sleep patterns were associated with alcohol use disorders in male who work night shift (OR: 1.74, 95% CI: 1.25–2.42) and in female who worked more than 52 hours per week (adjusted OR: 1.71, 95% CI: 1.04–2.80). Customized sleep management programs should be provided to workers in sleep-deprived working environments to prevent them from developing alcohol use disorders.


Introduction
Adequate sleep is essential for a healthy lifestyle for workers, but many workers struggle with insufficient sleep.In the United States, approximately 60% of workers experience sleep problems [1].According to a recent study, workers struggle to get enough sleep for an average 5.3 days per month [2].A study of South Korean workers found that short sleep duration of less than five hours was associated with high stress levels [3].A cohort study in the United Kingdom found an increased risk of death among workers who slept for less than seven hours per night [4].
Sleep problems are considered a major risk factor for occupational injuries among workers [5], and the cost of lost productivity is in the tens of billions of dollars [6]. Fatigue due to sleep deprivation is one of the main causes of traffic accidents, especially among transportation workers [7].Shift work increases the risk of fatigue-related errors and motor vehicle accidents while on the job or on the way home from work [8].In addition, workers who work overtime are also at an increased risk of on-the-job injuries due to reduced sleep duration [9].
Work-related stress, caused by heavy workloads [10], long working hours [11], adverse working conditions [12], and workplace conflicts [13], detrimentally affects sleep quality and sleep deprivation.Sleep deprivation adversely impacts the physical and mental health of workers [14] and can reduce work efficiency [15].Among workers, shift workers particularly face challenges with irregular schedules and circadian rhythm disruptions, increasing their susceptibility to sleep-related issues [16].Good sleep habit is crucial for developing healthy lifestyle practices [17].
Individuals who are sleep deprived often rely on alcohol to aid sleep [18], which is a notable practice among shift workers [19,20].Studies on the general population have shown that the use of alcohol a sleep aid is common [21].However, its use for sleep can gradually lead to harmful drinking habits [22].Alcohol use disorders can adversely affect the health of workers [23] and negatively impact social relationships [24].
Previous studies have primarily focused on how excessive alcohol use causes sleep problems [25,26].However, it is worth noting that workers who experience sleep deprivation may rely on alcohol to induce sleep.Research focusing on the general working population in this regard is limited.Investigating the relationship between sleep and alcohol use disorders among workers is necessary for public health and can contribute to long-term health prevention.Therefore, this study aimed to investigate the association between sleep patterns and alcohol use disorders among workers, with the goal of developing strategies for effective sleep management in this population.

Data and study population
We used data from the Korea National Health and Nutrition Examination Survey (KNHANES) conducted in 2014, 2016, 2018, and 2020.The KNHANES is a nationally approved statistical survey conducted annually by the Korea Centers for Disease Control and Prevention, and it aims to assess the health status and behaviors of the Korean population [27].Regarding this survey, data were collected from residents of South Korea aged one year and above.Households are chosen as survey participants according to specific criteria for each survey area each year.The health interview and examination items used in this study were conducted and provided, respectively, by trained medical professionals and interviewers [27].As the KNHANES adheres to the Declaration of Helsinki and offers de-identified data for public use, further ethical approval was not necessary for this study.
The total survey population included 31,051 respondents over the four-year period of 2014, 2016, 2018, and 2020.The classification of workers included those who answered "yes" to the question in the survey, "In the past week, have you worked for more than one hour for income, or have you worked as an unpaid family worker for more than 18 hours?".We included the data on only workers aged 19 years and above in the analysis.Any missing values for each survey item were excluded from the analysis (N = 1,317).The final analysis included data on 11,972 (6,472 male and 5,500 female) individuals (Fig 1).

Measures
The dependent variable in this study was alcohol use disorders as defined by the Alcohol use disorders identification test-consumption (AUDIT-C) questionnaire score.The AUDIT-C is an abbreviated version of the AUDIT, consists of the first three questionnaire of the AUDIT [28], and has high sensitivity and specificity in screening for alcohol use disorders [29].The AUDIT-C includes the following three questions about alcohol consumption in the past year: (1) frequency of drinking, (2) amount of alcohol consumed on a single occasion, and (3) frequency of binge drinking, with each question scored on a 0-4-point scale, totaling a score of 12 [28].As the standard alcohol drink differs in each country, the binge drinking questionnaire was based on the Korean standard, which defines binge drinking as more than seven drinks for male and more than five drinks for female in one drinking session, regardless of whether it being soju or hard liquor [30,31].In this study, we defined alcohol use disorders as an AUDIT-C score of 6 or more for male and 5 or more for female by referring to a previous study that measured thresholds using Korean data [32].
The independent variable was sleep patterns, which consisted of sleep quality and duration.Sleep quality was assessed using question 3 of the Patient Health Questionnaire-9, "In the past two weeks, have you had difficulty falling asleep, waking up for longer periods, or sleeping too much," and only those who answered "not at all" were classified as having good sleep quality [33].Sleep duration was defined as good if participants slept for seven or more hours, according to the recommended guidelines for optimal sleep duration in adults [34].Data on sleep duration was collected using a survey questionnaire, from which sleep hours were calculated.A participant was classified as having good sleep patterns if both sleep quality and sleep duration were good, and if either was not satisfactory, the person was considered to have poor sleep patterns.
The covariates were demographic factors, included age (19-29, 30-39, 40-49, 50 or older), education level (elementary school or less, high school, college or higher), and marital status (married, single).Socioeconomic factors included and region of residence (metropolitan, middle and small cities) and household income level (low, mid, high).We also included occupational type (white collar, pink collar, blue collar), shift type (daytime, night shift) and working hours (less than 40 hours per week, 40-52 hours, and more than 52 hours per week) to reflect the diversity of work types based on previous research [35][36][37].Health-related factors included smoking (yes, no), subjective health perception (low, mid, high), and perceived stress (low, high), and we further adjusted for whether respondents were advised by family members or doctors to cut back or stop drinking to control for the impact of alcohol use on sleep patterns.

Statistical analysis
The chi-squared test was used to examine the general characteristics of the participants.Multiple logistic regression analysis was used to examine the association of sleep patterns with alcohol use disorders, controlling for covariates.Further subgroup analyses stratified by sex and key independent variables were performed.Multinomial logistic regression was used to analyze the association between workers' sleep patterns and the severity of alcohol use disorders.The results of the analyses are expressed using odds ratios (ORs) and 95% confidence intervals (CIs).All statistical analyses were performed using SAS software version 9.4 (SAS Institute Inc., Cary, NC, USA), and a P-value<0.05was considered statistically significant.

Results
Table 1 presents the general characteristics of the respondents according to sex.The total sample was 11,972, of which 6,472 (54%) were male and 5,500 (46%) were female.Of the participants 55.6% (N = 3,599) of male and 51.8% (N = 3,353) of female had poor sleep patterns.Among workers with poor sleep patterns, alcohol use disorders were 57.7% (N = 2,076) for males and 29.5% (N = 988) for females.The association between sleep patterns and alcohol use disorders was significant in both males and females.Table 2 shows the results of the multiple regression analysis of the association between sleep patterns and alcohol use disorders after adjusting for covariates.Workers with poor sleep patterns had significantly higher odds of developing alcohol use disorder than those with good sleep patterns (male: adjusted OR 1.22 95% CI 1.07-1.39;female: adjusted OR 1.21, 95% CI 1.03-1.41).
Table 3 provides the results of the multiple regression analysis with subgroups stratified by the independent variables.Male shift workers with poor sleep patterns showed the highest association with alcohol use disorders (adjusted OR 1.74, 95% CI 1.25-2.42).Among female workers, poor sleep patterns were the most strongly associated with alcohol use disorders in Table 4 demonstrates the results of the multinomial logistic regression according to the severity of AUDIT-C score.Male workers with poor sleep patterns had higher odds of developing alcohol use disorders with increasing AUDIT-C scores than those with good sleep patterns (6-7 points: adjusted OR 1.10, 95% CI 0.93-1.30,8-9 points: adjusted OR 1.26, 95% CI 1.07-1.49,and 10-12 points: adjusted OR 1.40, 95% CI 1.16-1.69).Female workers showed a tendency for increased odds of alcohol use disorders as their AUDIT-C scores increased, but this was only statistically significant at scores between 10 and 12 (5-7 points: adjusted OR 1.19, 95% CI 0.99-1.43,8-9 points: adjusted OR 1.11, 95% CI 0.86-1.44,and 10-12 points: adjusted OR 1.73, 95% CI 1.17-2.54.

Discussion
This study used nationally representative data to define sleep quality and sleep duration as components of sleep patterns and examined their association with alcohol use disorders.After accounting for adjustment variables, workers with poor sleep patterns showed a higher association with alcohol use disorders.These results were significant for both males and females and were particularly pronounced among workers with poor sleep quality and sleep duration of seven hours or less.Therefore, it is important to consider sleep health as a factor in reducing alcohol use disorders among workers and to actively consider ways to manage both sleep quality and duration.
Previous studies of workers have primarily focused on the impact of work stress on sleep quality and duration [38,39].Work stress has also been identified as a major factor leading to alcohol use [40].However, this study sought to broaden the scope of worker healthcare by examining the link between poor sleep patterns and alcohol use disorders.In female workers in particular, a significant association with alcohol use disorders was observed even when sleep quality alone was poor.Females are more sensitive to sleep quality due to differences in role demands at home and work and vulnerability to stress than males, possibly increasing their susceptibility to alcohol use disorders [41,42].Additionally, female and older adults experience higher rates of severe insomnia [43].In our study, poor sleep patterns were highly correlated with alcohol use disorders among female workers over the age of 50 years and older.Therefore, the need for understanding workers' sleep habits in light of gender differences and intensive sleep hygiene education must be emphasized.We investigated whether the association between sleep patterns and alcohol use disorders differs according to working conditions.In male workers with night shifts, the association between poor sleep patterns and alcohol use disorders was found to be the highest.Working night shifts can disrupt circadian rhythms and reduce sleep quality [44] and may be associated with the use of alcohol to cope.One study found that alcohol use among shift workers could exacerbate unstable circadian rhythms [22].In addition, a previous study reported that working long hours was associated with alcohol use disorders [45].However, this association was primarily significant among female workers in our study.Long working hours due to high job demands can limit workers' sleep, which is important for recovery [46].Given previous research showing increased alcohol consumption among female workers with high job demands [47], the stress of working long hours may be linked to alcohol use among female workers.Therefore, it is important to proactively implement sleep hygiene interventions for workers in sleep-deprived work environments to prevent the onset of alcohol use disorders.
It is important to identify high-risk workers early to prevent sleep problems from becoming chronic and leading to alcohol use disorders.Light alcohol consumption before bedtime can help induce sleep in the short term, but this effect diminishes over time and can have negative long-term effects [48].High doses of alcohol can cause rapid eye movement sleep disruption, which can lead to a vicious cycle of sleep-related problems becoming chronic [49].In addition, programs aiming to promote sleep hygiene in workers need interventions that take the work environment into consideration.Job stress and lack of support at work can contribute to sleep problems [50,51], and active stress management programs are needed to manage these factors.This approach can help workers effectively manage workplace stress and maintain healthy sleep habits, contributing to their overall health.This study has several limitations.First, we used cross-sectional data to identify associations between sleep patterns and alcohol use disorders.Therefore, it is difficult to infer temporal causality.Second, the data used in our study were self-reported, which may affect the accuracy of measures related to sleep duration and quality.Third, although we used reliable instruments to measure alcohol use disorders, their cut-offs varied across studies.Therefore, further research using data from multiple countries is needed to verify our study findings.Fourth, although we controlled for demographic, socioeconomic, and health-related factors in our study, there may still be unmeasured confounding variables that could affect the results.For example, psychiatric conditions such as anxiety and depression can have a significant impact on sleep and alcohol use.Individuals with these disorders may use alcohol as a coping mechanism, which can affect their sleep patterns.In addition, use of substance such as psychotropic medications can alter sleep architecture and affect alcohol metabolism.However, due to limitations of the secondary data, these variables were not considered.

Conclusion
Poor sleep patterns among workers were associated with alcohol use disorders.Workers with poor sleep quality and less than seven hours of sleep were more likely to have alcohol use disorders.This association was higher among workers who worked night shifts or long hours, with differences according to gender.Therefore, customized sleep management programs tailored to workers with vulnerable working conditions are needed.Such programs should be designed considering gender-specific characteristics.

Table 2 . Results of factors associated with alcohol use disorders.
the results of the analysis of sleep patterns divided into sleep quality and sleep duration.Overall, workers with both poor sleep quality and poor sleep duration had increased odds of alcohol use disorders (male: adjusted OR 1.73, 95% CI 1.38-2.17;female: adjusted OR 1.44, 95% CI 1.13-1.84).Female workers had increased odds of alcohol use disorders even when only sleep quality was poor (adjusted OR 1.32, 95% CI 1.08-1.62).

Table 4 . The results of analysis stratified by severity of alcohol use disorders. Male Female Alcohol use disorders (AUDIT-C a score)
://doi.org/10.1371/journal.pone.0308418.t004 a AUDIT-C: Alcohol Use Disorders Identification Test-Consumption.b OR: odds ratio.c CI: confidence interval.https